(1 of )(SERENA WILLIAMS/ INSTAGRAM)

(2 of )FILE - In this May 1, 2017, file photo, Serena Williams, left, and Alexis Ohanian attend The Metropolitan Museum of Art's Costume Institute benefit gala in New York. Serena Williams says on social media that she gave birth to a baby girl named Alexis Olympia Ohanian Jr. The tennis star posted about the birth on her Instagram and Twitter accounts.
She says the baby was born on Sept. 1 and weighed 6 pounds, 14 ounces.(Photo by Evan Agostini/Invision/AP, File)

(3 of )FILE - This is a May 31, 2017, file photo showing Serena Williams watching her sister, Venus Williams, play against Japan's Kurumi Nara during a second round match at the French Open tennis tournament in Paris, France. Serena Williams says on social media that she gave birth to a baby girl named Alexis Olympia Ohanian Jr. The tennis star posted about the birth on her Instagram and Twitter accounts. She says the baby was born on Sept. 1 and weighed 6 pounds, 14 ounces. (AP Photo/Petr David Josek, File)

(4 of )FILE - In this May 31, 2017, file photo, Serena Williams watches her sister Venus Williams' match against Japan's Kurumi Nara during their second round match at the French Open tennis tournament in Paris, France. Serena Williams says on social media that she gave birth to a baby girl named Alexis Olympia Ohanian Jr. The tennis star posted about the birth on her Instagram and Twitter accounts. She says the baby was born on Sept. 1 and weighed 6 pounds, 14 ounces. (AP Photo/Petr David Josek, File)